1) Prepare Your Grill: FOR A GAS GRILL: If you have a grill that has more than one section, heat one section to high and one to medium. If you only have one section, heat it to medium. FOR A CHARCOAL GRILL: Use a chimmney starter to start you coals. When the coals in the starter are hot (all of the coals should start be turning grey and ash colored)-about 20-30 minutes-build a dual zone fire by piling all of the hot coals on one side of the grill. Move 3-4 of the hot coals to the empty side. Pour one layer of unburned coals over the hot ones (on the side with most of the coals-leave the two or three on the other side as they are). 2) Grill the Mushrooms: Place the cleaned portobello mushrooms into a small mixing bowl. Add 3 Tbsp. of the avocado or grapeseed oil, 3/4 tsp. fine sea salt, and 1 1/2 tsp. of the freshly ground black pepper and the 2 Tbsp. fresh sage to the portobellos and stir to combine (this is the "mushroom marinade"). Grill the mushrooms on the hot side of the grill, turning once until the grill marks both sides and they are cooked through but not burned (about 3-5 minutes per side). Remove the grilled mushrooms from the grill and place them back into the bowl with the mushroom marinade, and toss to coat completely. Set bowl with mushrooms into an ice bath (or into the freezer) to cool them quickly. When the mushrooms are cool enough to handle, remove them all from the bowl leaving any excess oil/her mixture in the bowl (do not discard). Finely chop (by hand) enough of the mushrooms to measure 1 cup, place them back into the bowl with the mushroom marinade and add the 1 Tbsp. balsamic glaze (this mixture will be added to the burgers in step #3 below). Thinly slice the rest of the mushrooms. Place 1 1/2 cups into another bowl and set aside (these will be added to the fondue in step #6 below). 3) Prepare the Burgers: Place the 4 oz. bacon into the bowl of a food processor and process until finely ground (1-2 minutes, on and off until evenly ground/chopped). Place the ground/chopped bacon into a large wide mixing bowl. Add the 1 cup finely chopped grilled mushrooms (from step #2 above), 2 Tbsp. porcini powder, 1 1/2 tsp. fine sea salt, 2 tsp. freshly ground black pepper and 3 Tbsp. minced fresh sage to the bacon. Use your hands to combine the mixture thoroughly (you want it uniformly and thoroughly mixed so when you add the beef you will not have to handle it any more than necessary). When the bacon and mushroom mixture is thoroughly combined, crumble the ground chuck over the mixture in the bowl and use your hands to toss the beef with the mixture-like a salad- crumbling the beef chunks as you mix. NOTE: You want to handle the meat as little as possible while still mixing it evenly and thoroughly. When mixed thoroughly, divide into 6 burgers/patties (a slightly rounded or "heaping" 3/4 cup meat mixture per burger-if you have a little meat mixture left over, make the chef a little spicy meat ball). Form each portion into a patty that is about 4 1/2" in diameter. Place burgers onto a clean platter and cover with plastic wrap. Chill while you make the Red Onion Slaw and prepare hte grill for the burgers. 4) For the Red Onion Slaw: Thinly slice the red onion and place it into a small mixing bowl. In another small bowl, combine the 1 cup Hellmann's Dinjonase mustard, 1/4 cup Dijon mustard, 1 tsp. fine sea salt, 1 tsp. freshly ground black pepper, and whisk or stir to combine thoroughly. Measure 12 Tbsp. of the mustard mixture into a small bowl, cover it with plastic and set aside (this will be spread onto the toasted buns in step #7 below). Set the remaining mustard mixture aside next to the bowl of sliced red onions (you will mix them at the last minute so the onions will stay crispy and fresh tasting). 5) Make the Herbed Mushroom Fondue: In a small mixing bowl toss the 1 1/2 cup of Gruyere with the cornstarch. Place the heavy cream into a deep heavy duty saucepan (it should be no more than 1/4 full so that when the cream boils it will not overflow into the grill), place onto the hot part of the grill and bring to a boil. Boil for about 5 minutes (being careful it doesn't burn or boil over), stirring constantly. Remove saucepan from the heat/grill and add the cheese/cornstarch mixture, using a whisk to combine thoroughly and melt the cheese evenly. Place back onto the heat for just a minute or two to bring it to a boil and to thicken the sauce (whisking constantly). Remove from the heat as soon as it boils and thickens, and stir in the grilled sliced mushrooms and minced fresh sage. Keep the fondue warm (on a cooler part of the grill) while you finish cooking and preparing the burgers. 6) Cook the Burgers: NOTE: Have a spray bottle filled with water ready (grill-side) when you cook the burgers to put out any flare-ups (flames) that result from the melting/dripping fat from the burgersl. Lightly oil both sides of all of the burgers; lightly oil the grill. Grill the burgers for about 4 minutes per side (you are aiming for about 135-140 degrees internal temperature-they will stay very juicy and moist because of the bacon and grilled mushrooms), turning them once. While the burgers cook, prepare the buns by scooping out a "divot" in each top bun, ie, remove excess dough from the inside of each top bun (not too much- leave enough bun as a shell to contain the burger)- this will help the Fondue and Slaw stay on the burger and help the burger stay together. Lightly oil the cut sides (including inside the "divot") of the top and bottom buns with avocado or grpaeseed oil. When the burgers are done, remove the burgers to a clean plate and tent with foil to rest and keep warm while you you toast the buns. Place the buns, cut sides down around the edges of the grill and cook for about 1-2 minutes, or until warm and lightly toasted. Remove buns from grill and place one top and bottom onto each of 6 plates. 7) Finish the Burgers: Spread about 1 Tbsp. of the mustard mixture (from the 12 Tbsp. which you have set aside in step #4 above) onto the cut sides of each top and bottom bun (spread it into the "divot" in the top buns). Toss the Red Onion mixture with the remaining mustard mixture. Place a cooked burger onto each bottom "divot" in each top bun and quickly flip the top bun onto the burger. Serves 6.